Germany

Bright spark solution

German wind turbine manufacturer GET Gesellschaft Energietechnik is paying particular attention to the problems of lightning protection. It reports useful information from recent lightning current impulse tests on wind turbine elements at the Laboratory of High Voltage Technology and Electromagnetic Compatibility at the Kiel Technical College. GET says the tests have revealed the importance of spark gaps. These can, for example, help shunt lightning charge across the hub and bearings to avoid both damage to the bearings and a dangerous voltage surge through inducing effects inside the nacelle.

GET stresses that a spark gap must be installed between the generator housing and the tower "as found in the A1200 1.2 MW Autoflug/GET turbine." A prototype of this machine was installed in October. Furthermore, the tips of the blades and the metal mesh must consist of low-impedance material and have sufficient thickness, continues GET, adding that the mesh has to be bedded into the gel coat of the blade and connected to the top of the blade with contacting areas of extremely low impedance. Finally GET points out that further investigation is required to fully understand many aspects of the lightning phenomenon, such as the nature of pre-discharging on stationary and moving blades.

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